Radical polymerization is an important commercial process for making a variety of polymers of vinyl monomers, such as acrylics and styrenics. While large amounts of polymers are made by this type of process, it does have some disadvantages, such as relatively poor control of polymer architecture. For instance, while molecular weight and/or molecular weight distribution may be controlled to some extent, close control of one or both of these parameters is usually difficult or impossible.
These parameters can be more closely controlled in so-called living-type polymerizations, but such polymerizations are unusual using radical polymerization methods. One such radical polymerization method is "atom transfer radical polymerization" (ATRP). In this process a transition metal (compound), usually in a lower valent state, is contacted with a compound which is capable of transferring an atom (radical) to the metal complex, thereby oxidizing the metal to a higher valent state and forming a radical which can initiate polymerization. However, at any time the atom that was transferred to the metal complex may be reversibly transferred back to the growing polymer chain, thereby forming a living polymerization system in which the molecular weight may be closely controlled and oftentimes the molecular weight distribution is narrow.
Such ATRPs are described in J -S. Wang, et al., J. Am. Chem. Soc., vol. 117, p. 5614-5615 (1995); J -S. Wang, Macromolecules, vol. 28, p. 7572-7573 (1995); M. Kato, et al., Macromolecules, vol. 28, p. 1721-1723 (1995); T. Patten, et al., Science, vol. 272, p. 866-868 (1996); C. Granel, et al., Macromolecules, vol. 29, p. 8576-8582 (1996); J -S. Wang, et al., Macromolecules, vol. 28, p. 7901-7910 (1995); V. Percec, et al., Macromolecules, vol. 29, p. 3665-3668 (1996); V. Percec, et al., vol. 28, p. 7970-7972 (1995); and World Patent Application WO 96/30421 which are all hereby included by reference. None of these references mention exposure of ATRPs to visible light.